Piezoelectricity of Nephila clavipes Dragline Silk

Piezoelectricity – Electrical potential (voltage) generated by mechanical stress. Nephila clavipes dragline silk is a protein-based natural fiber comprising a combination of disordered regions,omega-helices, and omega-pleated crystalline sheets. Dragline is 10-25% crystalline. Dragline, obtained from female Nephila clavipes spiders maintained in our laboratory, will be collected at 2, 2.5, 3, and 6 cm/s on a take-up reel powered by a DC motor. Samples will be tested for piezoelectricity using a modified DMTA (Dynamic Mechanical Thermal Analysis) apparatus to generate tension/release of the sample at selected frequencies over an appropriate temperature range. Resultant voltage across the sample will be measured using an electrometer. Structural data from NMR, SEM, AFM and X-ray diffraction will be used to make correlations between structure (crystallinity, orientation) and piezoelectricity of dragline silk.